Radio frequency weak magnetic field detection sensor and method of manufacturing the same

ABSTRACT

A radio frequency (RF) weak magnetic field detection sensor includes a ferromagnetic core, a pickup coil disposed to surround the ferromagnetic core, a substrate that includes an opening, a core pad connected to the ferromagnetic core and a coil pad connected to the pickup coil, and an insulating tube interposed between the ferromagnetic core and the pickup coil. The insulating tube includes a bobbin around which the pickup coil is wound, and a core hole formed to pass through the bobbin and configured to accommodate the ferromagnetic core.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of Korean Patent Application No.10-2020-0027602, filed on Mar. 5, 2020, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND 1. Field of the Invention

Example embodiments relate to a radio frequency (RF) weak magnetic fielddetection sensor, and a method of manufacturing the RF weak magneticfield detection sensor.

2. Description of Related Art

In general, there are many types of magnetic field sensors such as afluxgate sensor, a giant magneto-impedance (GMI) sensor, a giantmagneto-resistance (GMR) sensor, a hall effect sensor, an anisotropicmagneto-resistive sensor, and the like.

In particular, a radio frequency (RF) weak magnetic field sensor is asensor that is applicable to the fluxgate sensor and the GMI sensor, andis a magnetic field sensor that detects a magnitude of a relatively weakexternal magnetic field by using a soft magnetic material as a magneticcore. The RF weak magnetic field sensor is a reception sensor used formagnetic field communication in an extreme environment such asunderground and underwater. In order to receive a weak communicationsignal, the RF weak magnetic field sensor is required to be robust tonoise and have high sensitivity.

In addition, the fluxgate sensor and the GMI sensor are being developedin accordance with the trend of low power and miniaturization, and arewidely used in various fields such as military detection, aerospace,inertial navigation, biomedical identification, electronic compass,digital navigation, and a medical field.

In this regard, in order to have pico-Tesla level sensitivity that ishigh sensitivity, there are many difficulties in both theoretical andtechnical aspects. Currently, many methods are being attempted toimplement a pico-Tesla level high-sensitivity weak magnetic fieldsensor, such as a method for changing the number of windings of a pickupcoil, a method for approaching with a differential structure to reducenoise, a method for approaching through a feedback loop in a circuitalmanner, and the like.

SUMMARY

Example embodiments provide a radio frequency (RF) weak magnetic fielddetection sensor having a configuration capable of reducing noise andimproving sensor sensitivity, and a method of manufacturing the RF weakmagnetic field detection sensor.

In addition, example embodiments provide an RF weak magnetic fielddetection sensor having a configuration capable of achievingminiaturization and cost reduction, and a method of manufacturing the RFweak magnetic field detection sensor.

However, a technical aspect to be achieved by the example embodiments isnot limited to the above-described technical issues, and other technicalissues may exist.

According to an aspect, there is provided an RF weak magnetic fielddetection sensor including a ferromagnetic core, a pickup coil disposedto surround the ferromagnetic core, a substrate having an opening, acore pad connected to the ferromagnetic core, and a coil pad connectedto the pickup coil, and an insulating tube interposed between theferromagnetic core and the pickup coil. The insulating tube may includea bobbin around which the pickup coil is wound, and a core hole formedto pass through the bobbin and configured to accommodate theferromagnetic core.

A plurality of core holes may be formed to pass through the bobbin inparallel and spaced apart from each other.

The ferromagnetic core may include a plurality of amorphous wires formedwith an insulating coating on a surface thereof and accommodated side byside in the core hole.

Opposite ends of the ferromagnetic core may be formed with a platingportion that is formed of gold or silver and that is bonded to the corepad.

The pickup coil may include a first winding portion wound in a directionfrom one end of the bobbin toward another end of the bobbin, and asecond winding portion wound in a direction opposite to the firstwinding portion.

The substrate may further include an input pad connected to the core padon one side surface of the substrate and grounded on another sidesurface of the substrate, and an output pad connected to the coil pad onthe one side surface of the substrate and grounded on the other sidesurface of the substrate.

The substrate may have a via hole connected to the core pad or the coilpad on the one side surface and grounded on the other side surfacethrough the substrate. A region other than the core pad, the coil pad,the input pad, and the output pad may be grounded on the one sidesurface of the substrate.

A direction of an excitation magnetic field formed in the ferromagneticcore and a direction of an external magnetic field may be perpendicularto each other.

The RF weak magnetic field detection sensor may further include anexcitation coil wound around the ferromagnetic core. A direction of anexcitation magnetic field formed in the ferromagnetic core and adirection of an external magnetic field may be parallel to each other.

According to another aspect, there is provided a method of manufacturingan RF weak magnetic field detection sensor, the method including forminga first substrate by patterning a portion of a pickup coil on one sidesurface thereof and engraving a core hole on another side surfacethereof to accommodate a ferromagnetic core, forming a second substrateby patterning another portion of the pickup coil, a core pad, and a coilpad on one side surface thereof, and coupling the first substrate andthe second substrate to each other by connecting the portion and theother portion of the to pickup coil to each other, connecting theferromagnetic core and the core pad to each other, and connecting thecoil pad and the ferromagnetic core to each other by covering the firstsubstrate on the one side surface of the second substrate so that theferromagnetic core is accommodated in the core hole.

The method may further include forming a plating portion that is formedof gold or silver and that is bonded to the core pad at opposite ends ofthe ferromagnetic core.

The forming of the second substrate may further include forming a viahole connected to the core pad on one side surface and grounded onanother side surface through the substrate.

The forming of the first substrate may include forming a via hole in thefirst substrate to connect the portion of the pickup coil of the firstsubstrate and the other portion of the pickup coil of the secondsubstrate.

According to still another aspect, there is provided an RF weak magneticfield detection sensor including a ferromagnetic core, a pickup coildisposed to surround the ferromagnetic core, and an insulating tubeinterposed between the ferromagnetic core and the pickup coil. Theinsulating tube may include a bobbin around which the pickup coil iswound, and a plurality of core holes formed to pass through the bobbinin parallel and spaced apart from each other, the core holes beingconfigured to accommodate the ferromagnetic core.

The sensor may further include a substrate. The substrate may include anopening, a core pad connected to the ferromagnetic core, a coil padconnected to the pickup coil, an input pad connected to the core pad onone side surface of the substrate and grounded on another side surfaceof the substrate, and an output pad connected to the coil pad on the oneside surface of the substrate and grounded on the other side surface ofthe substrate.

The substrate may include a via hole connected to the core pad or thecoil pad on one side surface thereof and grounded on another sidesurface thereof through the substrate.

The ferromagnetic core may include a plurality of amorphous wires formedwith an insulating coating on a surface thereof and accommodated side byside in the core hole.

Opposite ends of the ferromagnetic core may be formed with a platingportion that is formed of gold or silver and that is bonded to the corepad.

The pickup coil may include a first winding portion wound in a directionfrom one end of the bobbin toward another end of the bobbin, and asecond winding portion wound in a direction opposite to the firstwinding portion.

According to still another aspect, there is provided an RF weak magneticfield detection sensor including a ferromagnetic core, a pickup coildisposed to surround the ferromagnetic core, and an insulating tubeinterposed between the ferromagnetic core and the pickup coil. Theinsulating tube may include a bobbin around which the pickup coil iswound, and a plurality of core holes formed to pass through the bobbinin parallel and spaced apart from each other, the core holes beingconfigured to accommodate the ferromagnetic core.

The substrate may include a via hole connected to the core pad or thecoil pad on one side surface thereof and grounded on another sidesurface thereof through the substrate.

The ferromagnetic core may include a plurality of amorphous wires formedwith an insulating coating on a surface thereof and accommodated side byside in the core hole.

Opposite ends of the ferromagnetic core may be formed with a platingportion that is formed of gold or silver and that is bonded to the corepad.

The pickup coil may include a first winding portion wound in a directionfrom one end of the bobbin toward another end of the bobbin, and asecond winding portion wound in a direction opposite to the firstwinding portion.

Additional aspects of example embodiments will be set forth in part inthe description which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

According to example embodiments, an RF weak magnetic field detectionsensor with reduced noise and improved sensitivity may be provided. Inaddition, according to example embodiments, an RF weak magnetic fielddetection sensor that is advantageous in miniaturization and is capableof reducing a cost for winding may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, features, and advantages of the inventionwill become apparent and more readily appreciated from the followingdescription of example embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a diagram illustrating a front surface and a rear surface of aradio frequency (RF) weak magnetic field detection sensor according toan example embodiment;

FIG. 2 is a diagram illustrating example embodiments of the insulatingtube and ferromagnetic core illustrated in FIG. 1 ;

FIG. 3 is a diagram illustrating example embodiments for improvingsensitivity of the RF weak magnetic field detection sensor illustratedin FIG. 1 ;

FIG. 4 is a diagram illustrating a characteristic of sensitivity basedon the number of amorphous wires in a condition in which an externalmagnetic field (4 μT) is applied;

FIG. 5 is a diagram illustrating a characteristic of a voltage inducedin a pickup coil based on an interval D between core holes in acondition in which an external magnetic field (50 μT) is applied;

FIG. 6 is a diagram illustrating other example embodiments for improvingsensitivity of the RF weak magnetic field detection sensor illustratedin FIG. 1 ;

FIG. 7 is a diagram illustrating an RF weak magnetic field detectionsensor according to another example embodiment by components; and

FIG. 8 is a diagram illustrating a front surface and a rear surface ofan RF weak magnetic field detection sensor according to another exampleembodiment.

DETAILED DESCRIPTION

Hereinafter, example embodiments will be described in detail withreference to the accompanying drawings. The scope of the right, however,should not be construed as limited to the example embodiments set forthherein. Various modifications may be made to the example embodiments.Here, examples are not construed as limited to the example embodimentsand should be understood to include all changes, equivalents, andreplacements within the idea and the technical scope of the exampleembodiments. The terminology used herein is for the purpose ofdescribing particular example embodiments only and is not intended to belimiting. As used herein, the singular forms “a,” “an,” and “the,” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood. that the terms“comprises,” “comprising,” “includes,” and/or “including,” when usedherein, specify the presence of stated features, integers, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, operations, elements,components, and/or groups thereof.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Unless otherwise defined, all terms, including technical and scientificterms, used herein have the same meaning as commonly understood by thoseskilled in the art to which the example embodiments pertain. Terms, suchas those defined in commonly used dictionaries, are to be interpreted ashaving a meaning that is consistent with their meaning in the context ofthe relevant art, and are not to be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Regarding the reference numerals assigned to the components in thedrawings, it should be noted that the same components will be designatedby the same reference numerals, wherever possible, even though they areshown in different drawings. Also, in the description of exampleembodiments, detailed description of well-known related structures orfunctions will be omitted when it is deemed that such description willcause ambiguous interpretation of the example embodiments.

FIG. 1 is a diagram illustrating a front surface and a rear surface of aradio frequency (RF) weak magnetic field detection sensor according toan example embodiment. FIG. 2 is a diagram illustrating exampleembodiments of the insulating tube and ferromagnetic core illustrated inFIG. 1 .

Referring to FIG. 1 , an RF weak magnetic field detection sensoraccording to an example embodiment may include substrates 100 a and 100b, a ferromagnetic core 101, an insulating tube 102, and a pickup coil103 a. The ferromagnetic core may be a most important parameter toimplement a weak magnetic field detection sensor, and may include a softmagnetic material.

The soft magnetic material may have characteristics such as a lowcoercivity in a hysteresis curve indicating a change in a magnetic fluxcaused by a magnetic material that is magnetized in response to a changein an external magnetic field, and a small magnetic loss caused by highsaturation magnetization and high permeability. The representative softmagnetic material may include MnZn and NiZn soft ferrites, permalloy(Ni80% Fe20%) alloy, cobalt and Fe amorphous metals, and the like. Thesoft magnetic material may have high permeability. In this exampleembodiment, a soft ferrite and a cobalt amorphous metal may be used as aferromagnetic core, and other soft magnetic materials such as permalloyalloy and the like may be used in place of the soft ferrite and thecobalt amorphous metal.

Referring to a process from 1 to 2 a of FIG. 2 , it can be confirmedthat the RF weak magnetic field detection sensor according to exampleembodiments is designed as an orthogonal fluxgate sensor having adirection in which an external magnetic field and an excitation magneticfield applied to the ferromagnetic core 101 are perpendicular to eachother. Specifically, the pickup coil 103 a may be wound around theferromagnetic core 101 in a circumferential direction, and no excitationcoil may exist. The orthogonal fluxgate sensor may be structurally thesame as an off-diagonal giant magneto-impedance (GMI) sensor, and theorthogonal fluxgate sensor and the off-diagonal GMI sensor may bedesigned and manufactured by the process from 1 to 2 a of FIG. 2 .

The ferromagnetic core 101 may be formed of the soft magnetic material,for example, a cobalt amorphous wire, and may have a circular crosssection having a diameter of 100 μm. When the pickup coil 103 a isformed by winding a coil in a manner of directly surrounding theamorphous wire, a high permeability characteristic may be broken due tostress of the amorphous wire, and magnetization may not be properlyperformed. In addition, when the coil is directly wound around theamorphous wire, the amorphous wire may be cut off or a winding coil maybe cut off during a winding process. Thus, it may be difficult toimplement the sensor, or a sensitivity characteristic may tend todeteriorate.

Therefore, in order to solve such problems, the insulating tube 102 maybe interposed between the ferromagnetic core 101 and the pickup coil 103a without directly winding the coil around the amorphous wire. Theinsulating tube 102 may include a bobbin 102 a around which the pickupcoil 103 a is wound, and a core hole 102 b formed to pass through thebobbin 102 a so as to accommodate the ferromagnetic core 101.

The pickup coil 103 a may be formed by winding the coil on the bobbin102 a. The bobbin 102 a may be formed of an insulator. The insulator mayinclude durable and heat-resistant plastic materials such as alumina,glass, silicone glass, quartz, polyether ether ketone (PEEK),polyolefin, and the like.

In consideration of a direction of a current flowing through the pickupcoil 103 a, the pickup coil 103 a may be wound in a left to rightdirection with respect to a first layer winding, and may be wound in aright to left direction with respect to a second layer winding after thefirst layer winding ends. That is, the pickup coil 103 a may include afirst winding portion wound in a direction from one end of the bobbin102 a toward another end of the bobbin 102 a, and a second windingportion wound in a direction opposite to the first winding portion.

By winding in a zigzag as described above, the pickup coil may be woundin the same direction as a direction in which a current flows throughthe coil, thereby increasing a magnitude of an induced magnetic flux. Ingeneral, it is possible to obtain an induced electromotive force inaccordance with Faraday's law from the pickup coil 103 a of the sensor,based on a principle of the weak magnetic field detection sensor.

${V_{i}(t)} = {{- \frac{d\phi}{dt}} = {{- {NA}}\frac{{dB}_{i}(t)}{dt}}}$

In the above equation, a cross-sectional area A of the ferromagneticcore 101 and the number of turns N of the wound pickup coil 103 a may beparameters for improving sensitivity of the sensor. Here, as the numberof turns N of the pickup coil 103 a increases, the sensitivity of thesensor may be improved. In this example embodiment, the sensor may beimplemented by varying the number of turns N of the pickup coil 103 a ofthe sensor. The desired number of turns N of the pickup coil 103 a maybe adjusted while stacking a first layer, a second layer, . . . , an Nlayer in a zigzag form. The pickup coil 103 a wound around the aluminainsulating tube 102 is illustrated in operation 1 of FIG. 2 . Forexample, with respect to the number of turns N of the pickup coil 103 a,it is possible to implement the pickup coil 103 a wound in the firstlayer with 250 turns and the pickup coil 103 a wound in the fifth layerwith 1250 turns.

Referring to FIG. 2 , a core hole 102 b with a penetrated interior maybe formed in the cylindrical alumina insulating tube 102. That is, thecore hole 102 b may be formed by an inner peripheral surface of thealumina insulating tube 102. An amorphous wire constituting theferromagnetic core 101 may be inserted into the core hole 102 b. Forexample, an inner diameter of the core hole 102 b may have a size of 100μm or more so that the amorphous wire is inserted, and an outer diameterof the bobbin 102 a may have a size of several mm or more. As a result,the alumina insulating tube 102 may have a structure in which theamorphous wire is inserted into the core hole 102 b that is a spaceformed in an inner diameter thereof, and the pickup coil 103 a is woundaround an outer diameter thereof.

Here, another parameter may be considered to improve the sensitivity ofthe weak magnetic field detection sensor. The number CN of amorphouswires (see FIGS. 3 and 4 to be described later) of the ferromagneticcore 101 may be increased, thereby improving output sensitivity of thesensor through a multi-core configuration. Specifically, theferromagnetic core 101 according to this example embodiment may includea plurality of amorphous wires accommodated side by side in the corehole 102 b by forming an insulating coating on a surface thereof.

For example, as illustrated in a right portion of operation 2 a of FIG.2 , it can be confirmed that two amorphous wires 101 are inserted intothe core hole 102 b of the alumina insulating tube 102, and the pickupcoil 103 a is wound around the bobbin 102 a. As described above, theweak magnetic field detection sensor may be configured to have amulti-core by increasing the number CN of amorphous wires constitutingthe ferromagnetic core 101.

Referring to FIG. 1 , it can be confirmed that there is a configurationin which the alumina insulating tube 102 into which the ferromagneticcore 101 is inserted is mounted on the PCB substrates 100 a and 100 bthrough soldering or the like. In this example embodiment, for example,the substrate may be an FR4 substrate having a relative permittivity(εr) of 4.5. The relative permittivity of the PCB substrates 100 a and100 b may not affect a magnetic sensor that detects a magnetic field.

Specifically, the substrate may have an opening 104 passing through acentral portion thereof in a rectangular shape. The alumina insulatingtube 102 into which the ferromagnetic core 101 is inserted may bepositioned in the opening 104.

In addition, the substrate may include core pads 106 a and 106 bconnected to the ferromagnetic core 101 and coil pads 107 a and 107 bconnected to the pickup coil 103 a. However, when the ferromagnetic core101 that is an amorphous wire is mounted on the core pads 106 a and 106b of the PCB substrates 100 a and 100 b by soldering, it may bedifficult to directly solder the amorphous wire to the core pads 106 aand 106 b due to its inherent characteristic. Accordingly, a platingportion formed of gold or silver for bonding to the core pads 106 a and106 b may be formed at opposite ends of the amorphous wire, and theplating portion may be bonded to the core pads 106 a and 106 b of thePCB substrates 100 a and 100 b by low-temperature soldering.

Opposite ends of the pickup coil 103 a wound around the aluminainsulating tube 102 may be connected to the coil pads 107 a and 107 bthrough soldering, respectively. The core pad 106 a may be connected toan input pad 105 a through a signal line formed on one side surface 100a of the substrate, and another side surface 105 b of the input pad 105a may be grounded GND. An SMA connector may be connected to the inputpads 105 a and 105 b.

In addition, the coil pads 107 a and 107 b connected to the pickup coil103 a may be connected to an output pad 108 a by the signal line formedon the one side surface of the substrate. Another side surface 108 b ofthe output pad 108 a may be grounded, and the SMA connector may beconnected to the output pads 108 a and 108 b.

The core pads 106 a and 106 b and the coil pads 107 a and 107 b may beconnected to a ground on a rear surface 100 b of the PCB substratethrough via holes 106 c and 107 c, respectively. In addition, a frontsurface 100 a of the PCB substrate also may be grounded GND, except thecore pads 106 a and 106 b, the coil pads 107 a and 107 b, the input pad105 a, the output pad 108 a, and the signal line. Accordingly, the RFweak magnetic field detection sensor according to example embodimentsmay secure the ground as much as possible on both the front and rearsurfaces 100 a and 100 b of the PCB substrate, thereby preventing theoccurrence of a drift problem of the weak magnetic field detectionsensor. That is, whereas a magnetic sensor generally fails to secure aground, and thus separates grounds of an input terminal and an outputterminal, the RF weak magnetic field detection sensor according toexample embodiments may use the grounds of the input terminal and theoutput terminal in common. Instead, the RF weak magnetic field detectionsensor may be configured to secure the ground as much as possible.

Referring to operation 2 b of FIG. 2 , the RF weak magnetic fielddetection sensor according to example embodiments may be designed as aparallel-type fluxgate sensor. The parallel-type fluxgate sensor may bea sensor having a direction in which an excitation magnetic field and anexternal magnetic field are parallel to each other.

The parallel-type fluxgate sensor may have a configuration in which asecondary coil (pickup coil 103 a) is wound around the outer diameter ofthe cylindrical bobbin 102 a, as illustrated in operation 1 of FIG. 2 .The bobbin 102 a may be formed of PEEK that is a plastic material. ThePEEK bobbin 102 a may have characteristics such as excellent durability,heat resistance, and chemical resistance.

In operation 2 b of FIG. 2 , the ferromagnetic core 101 may be formed ofa cylindrical soft magnetic Ni—Zn ferrite. In this case, for example,the Ni—Zn soft magnetic ferrite core may have a diameter of 5 mm and alength of 25 mm. In addition, the diameter and length may be changeddepending on the purpose.

In addition, an excitation coil 103 b that is a primary coil may bewound around the Ni—Zn ferrite core 101 in a left to right direction,for example. Further, the ferromagnetic core 101 around which theexcitation coil is wound may be inserted into the core hole 102 b formedin the insulating tube 102 formed of PEEK.

In this case, unlike the amorphous wire, the soft magnetic ferrite coremay have a characteristic that there is little influence resulting fromstress even when a coil with a diameter of several mm or more isdirectly wound around the core. In addition, the coil may be wound in azigzag, including the first winding portion and the second windingportion, in the same manner as illustrated in operation 2 a of FIG. 2 .

The ferromagnetic core 101 may include a single core or two or moremulti-cores. Even when configuring the parallel-type fluxgate sensor, inthe same manner as the orthogonal fluxgate sensor, an increase in thenumber CN of ferromagnetic cores (see FIGS. 3 and 6 to be describedlater) may improve the sensitivity of the sensor, and accordingly mayhave an effect of reducing noise of the sensor.

The RF weak magnetic field detection sensor according to this exampleembodiment may have a configuration in which the ferromagnetic core 101formed of a soft magnetic ferrite core and the excitation coil (primarycoil 103 b) wound directly around the ferromagnetic core 101 areinserted into the core hole 102 a formed in the bobbin 102 a formed ofPEEK, and the pickup coil (secondary coil 103 a) is wound around thebobbin 102 a formed of PEEK. In this case, the primary coil 103 b may beused as an input terminal that applies a current, and the secondary coil103 a may be used as an output terminal that outputs an induced voltage.

FIG. 3 is a diagram illustrating example embodiments for improvingsensitivity of the RF weak magnetic field detection sensor illustratedin FIG. 1 . FIG. 4 is a diagram illustrating a characteristic ofsensitivity based on the number of amorphous wires in a condition inwhich an external magnetic field (4 μT) is applied. The RF weak magneticfield detection sensor according to example embodiments may haveimproved sensitivity by a structural design of an insulating tube, asillustrated in FIG. 3 .

Specifically, the multi-core may be configured by changing the number CNof the core holes 102 b provided in the insulating tube 102 to 1, 2, 3,. . . , N, and correspondingly increasing the number CN of theferromagnetic cores 101. That is, the number CN of the core holes 102 bformed to pass through the bobbin 102 a may represent the number CN ofthe ferromagnetic cores 101. In general, when the number offerromagnetic cores 101 increases, the sensitivity may tend toexponentially increase, as illustrated in FIG. 4 , and noise of thesensor may decrease. As illustrated in FIG. 3 , a configuration andarrangement of the core hole 102 b may be configured in variouscombinations such as a horizontal structure, a vertical structure, a anda structure in which the horizontal structure and the vertical structureare combined.

The core hole 102 b of the alumina insulating tube 102 may be formed tohave a size several times larger than a diameter of an amorphous wirethat is the ferromagnetic core 101. In addition, N amorphous wires 101may be inserted into the core hole 102 b at once by increasing thenumber CN of amorphous wires. The multi-core may be configured in such astructure, thereby improving the sensitivity.

In this case, in the N amorphous wires included in the ferromagneticcore 101, magnetization may cause interaction with each other, and thusthe sensitivity may increase exponentially as illustrated in FIG. 4 .Therefore, in this example embodiment, it is possible to prevent acharacteristic of the amorphous wire from being changing by using aglass-coated amorphous wire. That is, the amorphous wire may be coatedwith an insulator to maintain its inherent characteristic.

Furthermore, as can be seen from Faraday's law of induction, as thecross-sectional area A of the ferromagnetic core 101 increases, thesensitivity of the sensor may be improved. A size S of a bobbinaccording to example embodiment may also affect an improvement insensitivity.

For example, a diameter S of the alumina insulating tube 102 used as theinsulator bobbin of FIG. 3 also may be a parameter for improvingsensitivity. The pickup coil 103 a may be wound around an outerperipheral surface of the alumina insulating tube 102 (bobbin 102 a),and the ferromagnetic core 101 may be inserted into the core hole 102 bof the alumina insulating tube 102. Therefore, an interval between thecore and the pickup coil 103 a may be important.

The interval may be associated with the diameter S of the aluminainsulating tube. When a current is applied to the core and an externalmagnetic field is applied to the core, magnetization may occur, and aresulting change in a magnetic flux may be detected by the pickup coilto obtain an induced electromotive force. A distance (interval) betweenthe ferromagnetic core 101 and the pickup coil 103 a may be an importantfactor for improving sensitivity. In other words, a size of the bobbin102 a, for example, a size S of the alumina insulating tube, may bereferred to as a parameter for improving sensitivity, and the size S ofthe bobbin 102 a may be optimized while performing a proper adjustmentsuch as reduction or increase.

In addition, in FIG. 3 , when the number CN of the core holes 102 b ofthe alumina insulating tube 102 is plural, the interval D between thecore holes 102 b also may be an important parameter for improving thesensitivity of the sensor. The interval D between the core holes 102 bmay be applied in the same manner when configuring the parallel-typefluxgate sensor in operation 2 b of FIG. 2 . The interval D between thecore holes 102 b of the PEEK bobbin 102 a used in operation 2 b of FIG.2 may be an important parameter for improving the sensitivity of thesensor.

FIG. 5 is a diagram illustrating a characteristic of a voltage inducedin a pickup coil based on an interval D between core holes in acondition in which an external magnetic field (50 μT) is applied.Referring to FIG. 5 , in a parallel-type fluxgate sensor including twosoft magnetic ferrite cores, a simulation result based on a change inthe interval D between the two cores can be confirmed.

A parameter D of FIG. 5 may represent an interval between the core holes102 b of the PEEK bobbin 102 a, and may also represent the interval Dbetween the ferromagnetic cores 101 since the soft magnetic ferrite coreis inserted into the two core holes 102 b. Referring to FIG. 5 , it canbe confirmed that the shorter the interval D is, the greater an inducedvoltage of the pickup coil 103 a wound around the outer diameter of thePEEK bobbin 102 a. Therefore, it can be confirmed that the interval D isa parameter that affects an improvement in the sensitivity of thesensor. That's because, when there are a plurality of cores in theprocess of magnetizing the ferromagnetic core 101, an amount ofmagnetization may vary depending on the interval D between the cores. Inother words, the pickup coil may detect a change in a magnetic fluxoccurring when the plurality of cores are magnetized by the interval D,and an amount of change in the magnetic flux may vary, and accordinglyan amount of change in the induced voltage may vary.

FIG. 6 is a diagram illustrating other example embodiments for improvingsensitivity of the RF weak magnetic field detection sensor illustratedin FIG. 1 . FIG. 6 illustrates a shape of an insulator configureddifferently from that of FIG. 3 . In FIG. 3 , the bobbin 102 a that aninsulator may have a cylindrical alumina insulating tube shape. In theexample embodiment of FIG. 6 , a cross section of the bobbin 102 c maybe configured in a square form.

In addition, a shape of the insulator that is a bobbin may have acylindrical shape, a square column shape, a hexagonal column shape, andthe like, and a size S of the bobbin 102 c with the same shape may bealso changed as illustrated in FIG. 6 to improve the sensitivity of thesensor. The number CN and configuration of holes for configuring amulti-core may vary depending on the size S and structure of the bobbin102 c.

In the above, the RF weak magnetic field detection sensor configured asa bulk type according to an example embodiment has been described withreference to FIGS. 1 to 6 . Hereinafter, a thin film-type RF weakmagnetic field detection sensor according to another example embodimentwill be described with reference to FIGS. 7 and 8 .

FIG. 7 is a diagram illustrating an RF weak magnetic field detectionsensor according to another example embodiment by components. FIG. 8 isa diagram illustrating a front surface and a rear surface of an RF weakmagnetic field detection sensor according to another example embodiment.

According to example embodiments, a first substrate 200 a of operation 1of FIG. 7 and second substrates 203 a and 203 b of operation 2 of FIG. 7may be used as components to configure a weak magnetic field detectionsensor having improved sensitivity. A difference between this exampleembodiment and a previous example embodiment is that a pickup coil maybe patterned. In a method for implementing a pickup coil by winding acoil, it may be disadvantageous in miniaturization of the weak magneticfield detection sensor, and the coil may be cut off during a coilwinding process, and a precision winding may be performed using awinding machine, resulting in a large cost. Such problems may beeffectively solved by patterning the pickup coil according to anotherexample embodiment.

In operation 1 a of FIG. 7 , N pickup coils 201 a 0 may be patterned ona front surface 200 a of a first PCB substrate. That is, in an operationof forming a first substrate, a portion 201 a 0 of the pickup coil maybe patterned on one side surface 201 a of the first substrate.

A via hole 201 b 0 may be formed in a coil pad provided at an edge ofthe patterned pickup coil 201 a 0, and the patterned pickup coil 201 a 0may be connected to a coil pad 201 a 1 of a pickup coil 201 a 2 of asecond PCB substrate 203 a to be described later. The patterned pickupcoil 201 a 0 may be connected to the patterned pickup coil 201 a 2 ofthe second PCB substrate 203 a by the coil pad 201 a 1. Accordingly, allof the pickup coils 201 a 0, 201 b 0, 201 a 1, and 201 a 2 may beconnected to one another.

A rear surface 200 b of the first PCB substrate of FIG. 7 may be formedas in operation 1 b or operation 1 c to improve sensitivity. That is, inan operation of forming the first substrate, a core hole may be engravedso as to accommodate the ferromagnetic core 101 on another side surface201 b of the first substrate.

In operation 1 b of FIG. 7 , the rear surface 200 b of the first PCBsubstrate may be engraved 202 in a straight line to configure amulti-core. For example, five engravings 202 spaced side by side may beformed. In this case, the engraving may be formed several μm deeper thana depth of 100 μm so that the amorphous wire 101 of 100 μm that is aferromagnetic core is inserted. Multi-cores may be configured inparallel by inserting the amorphous wire 101 as much as the number CN ofengravings, thereby improving sensitivity of the sensor and reducingnoise of the sensor.

Operation 1 c of FIG. 7 , which is another method for configuring amulti-core, may form one engraving 202 on the rear surface 200 b of thefirst PCB substrate. By setting the number CN of engravings as one andincreasing an engraved area, as illustrated in a lower portion ofoperation 1 c, a plurality CN of amorphous wires 101 may be inserted,thereby reducing the noise of the sensor and improving the sensitivityof the sensor.

In an operation of forming a second substrate, another portion 201 a 2of the pickup coil, core pads 206 a and 206 b, and the coil pad 201 a 1may be patterned on one side surface 203 a of the second substrate.Further, an input pad 204 a connected to the core pads 206 a and 206 band an output pad 205 a connected to the coil pad 201 a 1 may be formed.

Referring to operation 2 of FIG. 7 , the second PCB substrates 203 a and203 b may include N coil pads 201 a 1 connected to the patterned Npickup coils 201 a 2, the input pad 204 a, the core pads 206 a and 206 bconnected to the input pad along a signal line, and the output pad 205 aconnected to the coil pad 201 a 1. One of the two core pads 206 a and206 b may be formed with a plurality of via holes 201 b 1 for connectionto a ground of the rear surface 203 b of the second PCB substrate, andmay be connected to the ground of the rear surface 203 b of the secondPCB substrate. In addition, an SMA connector may be connected to theinput pads 204 a and 204 b and the output pads 205 a and 205 b on thefront and rear surfaces 203 a and 203 b of the second PCB substrate.

FIG. 8 illustrates an RF weak magnetic field detection sensor completedby combining first substrates 200 a and 200 b and second substrates 203a and 203 b, and two PCB substrates may be assembled by soldering, forexample. Specifically, the RF weak magnetic field detection sensor mayhave a structure in which the rear surface 200 b of the first PCBsubstrate is covered by and coupled to the front surface 203 a of thesecond PCB substrate. Connection between the amorphous wire 101 that isa ferromagnetic core and the core pads 206 a and 206 b may be performedby forming gold or silver plating on opposite ends of the amorphous wire101, and performing low-temperature soldering on the plated amorphouswire and the core pads. According to such a structure, the weak magneticfield detection sensor may be implemented to have a structure in whichall patterned pickup coils of the first PCB substrate and the second PCBsubstrate are connected while N ferromagnetic cores 101 are insertedbetween the connected pickup coils to configure a multi-core.

The components described in the example embodiments may be implementedby hardware components including, for example, at least one digitalsignal processor (DSP), a processor, a controller, anapplication-specific integrated circuit (ASIC), a programmable logicelement, such as a field programmable gate array (FPGA), otherelectronic devices, or combinations thereof. At least some of thefunctions or the processes described in the example embodiments may beimplemented by software, and the software may be recorded on a recordingmedium. The components, the functions, and the processes described inthe example embodiments may be implemented by a combination of hardwareand software.

A number of example embodiments have been described above. Nevertheless,it should be understood that various modifications may be made to theseexample embodiments. For example, suitable results may be achieved ifthe described techniques are performed in a different order and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents.

Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A radio frequency (RF) weak magnetic fielddetection sensor comprising: a ferromagnetic core; a pickup coildisposed to surround the ferromagnetic core; a substrate having anopening, a core pad connected to the ferromagnetic core, and a coil padconnected to the pickup coil; and an insulating tube interposed betweenthe ferromagnetic core and the pickup coil, wherein the insulating tubecomprises: a bobbin around which the pickup coil is wound; and a corehole formed to pass through the bobbin, the core hole being configuredto accommodate the ferromagnetic core, wherein a plurality of core holesare formed to pass through the bobbin in parallel and spaced apart fromeach other, wherein the pickup coil comprises: a first winding portionwound in a direction from one end of the bobbin toward another end ofthe bobbin; and a second winding portion wound in a direction oppositeto the first winding portion, wherein the substrate further comprises:an input pad connected to the core pad on one side surface of thesubstrate, and grounded on another side surface of the substrate; and anoutput pad connected to the coil pad on the one side surface of thesubstrate, and grounded on the other side surface of the substrate. 2.The RF weak magnetic field detection sensor of claim 1, wherein theferromagnetic core comprises a plurality of amorphous wires formed withan insulating coating on a surface thereof and accommodated side by sidein the core hole.
 3. The RF weak magnetic field detection sensor ofclaim 1, wherein opposite ends of the ferromagnetic core are formed witha plating portion that is formed of gold or silver and that is bonded tothe core pad.
 4. The RF weak magnetic field detection sensor of claim 1,wherein the substrate has a via hole connected to the core pad or thecoil pad on the one side surface and grounded on the other side surfacethrough the substrate.
 5. The RF weak magnetic field detection sensor ofclaim 4, wherein a region other than the core pad, the coil pad, theinput pad, and the output pad is grounded on the one side surface of thesubstrate.
 6. The RF weak magnetic field detection sensor of claim 1,wherein a direction of an excitation magnetic field formed in theferromagnetic core and a direction of an external magnetic field areperpendicular to each other.
 7. The RF weak magnetic field detectionsensor of claim 1, further comprising: an excitation coil wound aroundthe ferromagnetic core, wherein a direction of an excitation magneticfield formed in the ferromagnetic core and a direction of an externalmagnetic field are parallel to each other.
 8. A radio frequency (RF)weak magnetic field detection sensor comprising: a ferromagnetic core; apickup coil disposed to surround the ferromagnetic core; an insulatingtube interposed between the ferromagnetic core and the pickup coil; anda substrate, wherein the insulating tube comprises: a bobbin aroundwhich the pickup coil is wound; and a plurality of core holes formed topass through the bobbin in parallel and spaced apart from each other,the core holes being configured to accommodate the ferromagnetic core,wherein the substrate comprises: an opening; a core pad connected to theferromagnetic core; a coil pad connected to the pickup coil; an inputpad connected to the core pad on one side surface of the substrate, andgrounded on another side surface of the substrate; and an output padconnected to the coil pad on the one side surface of the substrate, andgrounded on the other side surface of the substrate, wherein the pickupcoil comprises: a first winding portion wound in a direction from oneend of the bobbin toward another end of the bobbin; and a second windingportion wound in a direction opposite to the first winding portion. 9.The RF weak magnetic field detection sensor of claim 8, wherein thesubstrate comprises a via hole connected to the core pad or the coil padon one side surface thereof and grounded on another side surface thereofthrough the substrate.
 10. The RF weak magnetic field detection sensorof claim 8, wherein the ferromagnetic core comprises a plurality ofamorphous wires formed with an insulating coating on a surface thereofand accommodated side by side in the core hole.
 11. The RF weak magneticfield detection sensor of claim 8, wherein opposite ends of theferromagnetic core are formed with a plating portion that is formed ofgold or silver and that is bonded to the core pad.